11
votes
Vertical Datum conversion of a raster with gdal
Convert from (EGM96) geoid vertical datum to (WGS84) ellipsoid vertical datum:
gdalwarp -s_srs "+proj=longlat +datum=WGS84 +no_defs +geoidgrids=egm96_15.gtx" -t_srs "+proj=longlat +...
- 111
10
votes
How does a Spatial Reference System like WGS84 have an elipsoid and a geoid?
WGS84 is natively XYZ, like the International Terrestrial Reference Frames (ITRF), and you can use an ellipsoid model to convert to latitude, longitude, and ellipsoidal height. Ellipsoidal heights ...
- 19.1k
9
votes
Where does the Geoid information in a GPS unit come from?
GPS units can be pre-loaded with one or more geoids, which can be used to calculate elevations by geoid separation. But support for this feature varies by manufacturer and by device.
On many Trimble ...
- 12.3k
6
votes
Converting LiDAR ellipsoidal heights to orthometric heights?
PDAL can do this with its filters.reprojection capability, which is based on the vertical datum transformation capabilities of Proj.4.
pdal translate input.las output.las reprojection
--filters....
- 4,106
5
votes
Accepted
Can QField record GPS Z-Value
QField can record z value from NMEA sentence. Create a layer, then save as, select geometry type and flag include z-dimension.
I use it with an RTK GNSS. I collect point, lines (I have not try with ...
4
votes
How does Ellipsoidal Height and Geoidal Height impact water flow?
Earth's surface is often represented as an ellipsoid and an ellipsoid is just an oblate sphere. What controls water flow is the relief and topography of the earth under the rules of gravity (or more ...
4
votes
How does a Spatial Reference System change the underlying geoid without having to update coordinates?
Updated EPSG information as of February 27, 2021. Check the edit history for the previous version. Updated by mkennedy.
The Wikipedia article is out of date. The current WGS84 geoid model is EGM2008 ...
- 19.1k
4
votes
Accepted
Using local mean sea level (LMSL) as altitude for converting latitude longitude altitude to ECEF
To convert from orthometric (vertical datum-based) heights to ellipsoidal heights, you need to add the geoid height to your Google Map elevations. I am not exactly sure how Google uses LMSL, it might ...
- 3,866
3
votes
Where does the Geoid information in a GPS unit come from?
Unless otherwise specified, a GPS unit is probably using the WGS84 ellipsoid and EGM96 geoid, and the separation it reports is the vertical distance between those two surfaces at the present latitude ...
- 131
3
votes
Accepted
WGS84 to MSL and opposite
I think there is a problem with the way you are thinking about the whole thing.
To sum up:
You use Cesium points which are from a Digital Elevation Model. Those points are expressed in WGS84 and the ...
- 326
3
votes
Find gravity normal by ECEF or GPS coordinate of point
I realise this is an old thread now but for future reference Earth is represented as a type of ellipsoid called an oblate spheroid. The oblate spheroid is a result of the balancing between self ...
- 31
3
votes
Accepted
Calculating Geoid Height (e.g. EGM2008) for Lat/Lon in PostGIS
Calculating, No. Looking up, Yes.
Pre-calculated data is available for the various Geoid models (EGM84, EGM96, EGM2008) in raster format. Here's an easy to use source:
https://sourceforge.net/...
- 872
2
votes
How does a Spatial Reference System like WGS84 have an elipsoid and a geoid?
The text is not accurate. GRS80 and WGS84 describe really the ellipsoid only, they are not directly linked to any geoid as the text suggests.
But as the elevation above WGS84 elipsoid is not really ...
- 426
2
votes
How does a Spatial Reference System like WGS84 have an elipsoid and a geoid?
When measuring heights, there should be an initial point or zero point as reference for measuring. That is where the Geoid and Ellipsoid fits in. The Ellipsoid and Geoid are considered the initial ...
- 345
2
votes
What is elevation relative to in EPSG:2284?
EPSG:2284 only specifies the horizontal coordinates, the altitudes depend on the system the surveyor (or whoever captured the points) used. It could be in NAVD88, Mean Sea Level, etc. You'll have to ...
- 7,873
2
votes
Are LiDAR datasets with same vertical datum, but based on different geoids comparable?
LiDAR measurements are in the ellipsoidal height system. First, you have to see if the two sets use the same ellipsoidal system. I think the answer is yes and the system should be WGS84 (the GPS ...
- 21
2
votes
Are LiDAR datasets with same vertical datum, but based on different geoids comparable?
To accurately compare these two LiDAR datasets do I need to update the old dataset to use the new geoid?
Yes, the two geoid models will have different ondulation values for different same coordinates ...
- 174
2
votes
Converting elevation from EU-DEM (ETRS89) to WGS84
For those facing this problem, use the new DEM (Digital Elevation Model) instead, also from Copernicus.
The latest DEM GeoTIFF files from Copernicus not only are available in WGS84, but also give you ...
2
votes
Accepted
Using NAVD88 geoid in Northern Canada?
Is there an issue with calculating the offsets in Northern Canada? Are the gtx files even defined there?
If you open up the *.gtx files in QGIS, for example, you'll find that they are not defined ...
- 71
2
votes
Adding local geoid in ArcGIS Desktop?
Right now, there isn't a custom vertical transformation tool which would let the software know how to handle the local geoid file.
If the geoid file is in either US National Geodetic Survey's geoid ...
- 19.1k
2
votes
Convert Geoid File Types
You can download a demo verion of the Hydromagic software from https://www.eye4software.com/download/
It includes a geoid converter freeware: https://www.eye4software.com/hydromagic/documentation/...
- 77.1k
2
votes
Which height data is correct?
It appears that the altitude values from your bird-mounted GNSS unit are returning heights in WGS84 geoid heights. Here is a nice tutorial on vertical datums. I see from the link you posted that the ...
- 10.5k
2
votes
Accepted
Convert XYZ file with WGS84 Ellipsoid elevations to EGM96 Geoid elevations
The United States National Oceanic and Atmospheric Administration distributes a freeware package called vDatum for doing vertical datum transformations. vDatum is a Java executable file so there are ...
- 10.5k
1
vote
Gravity related height from ellipsoidal height using pyproj
From projinfo application of the PROJ library:
c:\>projinfo -s EPSG:4979 -t EPSG:7417
returns:
Operation n1:
unknown id, Inverse of DVR90 height to ETRS89 + Inverse of ETRS89 to WGS 84 (1)...
- 14.7k
1
vote
Transform datum CSV->CSV using ogr2ogr
Since I could not get ogr2ogr to work using a VRT-file I used Python to loop through a CSV file using gdaltransform. The procedure is as follows:
Source CSV format for data_wgs84.csv:
id,E,N,Z,Lat,...
- 91
1
vote
Transform datum CSV->CSV using ogr2ogr
On the GDAL-DEV mailing list I was kindly adressed to install vertical datum grids for GDAL. I did not achieve this under Windows using installers from gisinternal. On Ubuntu though I followed hints ...
- 91
1
vote
Accepted
How to calculate the distance to the Earth center if I know the elevation above the reference geoid?
The linked image shows the EGM96 geoid, which is the undulation of the geoid, or the distance between the geoid and the reference ellipsoid, which I believe is the WGS84 ellipsoid. The minimum ...
- 2,150
1
vote
Downloading geoid chgeo2004?
Not the official source, but working:
https://www.eye4software.com/files/geoids/CHGEO04A.zip from Eye4software
You can download a demo verion of the Hydromagic software from https://www.eye4software....
- 77.1k
1
vote
Convert Geoid File Types
GDAL will support BYN files in an upcoming release. However, it is unclear when this release will be compiled for windows.
In the meantime, I've uploaded converted GTX files for HT2_0 and CGG2013 so ...
- 434
1
vote
Vertical Datum conversion of a raster with gdal
See the direct function (dem_geoid) for geoid conversion available in the NASA Ames Stereo Pipeline(https://ti.arc.nasa.gov/tech/asr/groups/intelligent-robotics/ngt/stereo/).
Only top scored, non community-wiki answers of a minimum length are eligible